This package provides an online coordination method for multiple robots for use with the navigation_oru package. It is based on the coordination_oru implementation of a trajectory-envelope based coordination algorithm.

This package requires ROS Kinetic or Indigo on Ubuntu 16.04 or 14.04 (see here for instructions), the navigation_oru package (see here for instructions), and ROSJava (please follow the instructions for your ROS distribution here).

This package also requires the coordination_oru library, however this is included as a submodule in this GIT repository, so no special steps are necessary to install it (see below).

After installing ROS, ROSJava, and the navigation_oru package as instructed above, clone this repository into your Catkin workspace and compile the source code with catkin_make (which in turn runs a gradle build, redistributable included):

$ cd catkin_ws/src
$ git clone --recursive https://github.com/FedericoPecora/coordination_oru_ros.git
$ cd ..
$ catkin_make
$ source devel/setup.bash

Please note: do not omit the --recursive flag in the clone command above, as this is responsible for including the coordination_oru library in the build.

In order to automatically pull changes in coordination_oru whenever you pull coordination_oru_ros, you can add the following alias:

$ git config alias.spull '!git pull && git submodule update --remote --merge'

This way, both repositories will be pulled whenever you issue the command

$ git spull

Two launch files are provided, one involving a single robot, and one involving three robots. The single robot example is launched as follows:

$ roslaunch coordination_oru_ros single_truck.launch

This will bring up an rviz window from which goals can be posted for robot via the "2D Nav Goal" button located on the top bar. Each time a goal is posted, the path is computed via a call to the ComputeTask service, and dispatched to the vehicle_execution_node via a call to the ExecuteTask service. The example does not involve coordaintion (as there is only one robot), and is meant to show how these services are called by the MainNode.java ROS node. The external behavior of the system is identical to that of the single_truck.launch launch file provided as an example in the navigation_oru package.

The following launch file starts an example with three robots:

$ roslaunch coordination_oru_ros multiple_trucks.launch

The launch file opens an rviz window from which one can post goals for any of the three robots (via the three "2D Nav Goal" buttons on top). Goals can be posted online, and the movements of the robots will be coordinated according to the coordination algorithm implemented in the coordination_oru package (see here for a brief explanation of the algorihtm). The method relies on the ability of the vehicle_execution_node to accept task updates with a critical point, that is, an index of a pose along a robot's reference trajecotry beyond which the robot should not proceed. The coordination algorithm computes these critical points online and updates the tasks executed by the vehicle_execution_nodes via calls to the ExecuteTask service with the update flag set to true (see method setCriticalPoint(int arg0) in class TrajectoryEnvelopeTrackerROS).

The images below show three moments during the coordinated navigation of the three robots.

The coordinator should be provided the following paramteres (see also example launch files):

• robot_ids: the list of identifiers of robots that are subject to coordination

• footprint_rear_left_x, footprint_rear_left_y etc.: coordinates that define the footprint of the robots, in meters

• control_period: the period at which the coordinator updates the critical points of the robots

• temporal_resolution: the temporal resolution at which the control_period is expressed (1000.0 if the control_period is in milliseconds)

• forward_model_max_accel: the (constant) acceleration used in the forward model, in m/s^2

• forward_model_max_vel: the maximum velocity used in the forward model, in m/s

coordination_oru_ros - Online coordination for multiple robots with ROS

Copyright (C) 2017 Federico Pecora, Henrik Andreasson

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.